Formamidinium lead bromide and iodide (FAPbX₃, X = Br, I) in the form of colloidal nanocrystals (NCs) exhibit outstanding photoluminescence properties in the green and infrared regions of the electromagnetic spectrum, characterized by narrow emission line widths (below 90 meV) and high quantum yields (above 90%). The controlled formation of Br-I mixed halide NCs is a facile strategy for tuning band-gap energies, in particular between 700 and 800 nm, not accessible with CsPbX3 NCs. Herein, we report a mechanistic and high-throughput parametric screening study of the synthesis of such NCs using droplet-based microfluidic platforms, equipped with in situ optical characterization. We establish the growth conditions that fully suppress the formation of nanoplatelet impurities in the final colloid and demonstrate that the formation mechanism of FAPbBr₃ NCs proceeds via the formation of nanoplatelets as transient species, whereas FAPbI₃ forms directly as cubic-shaped NCs. In contrast to CsPb(Br/I)₃ NCs, the stability of FAPb(Br/I)₃ NCs increases with iodine content. Such NCs form by first nucleating pure FAPbI₃ NCs, followed by incorporation of bromide ions.

中文翻译：

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微流控反应器为甲ami鎓卤化钙钛矿纳米晶体的合成提供了制备和机理上的见解

甲ami溴化铅和碘化物（FAPbX ₃，X = Br，I）胶态纳米晶体（NCs）的形式在电磁光谱的绿色和红外区域表现出出色的光致发光特性，其特征是发射线宽度窄（低于90 meV）和高量子产率（高于90％ ）。Br-1混合卤化物NCs的受控形成是调节带隙能量（尤其是在700至800 nm之间）的便捷策略，CsPbX3 NCs无法获得。在这里，我们报告了使用基于液滴的微流控平台并配备有原位光学表征技术的此类NC合成的机械化和高通量参数筛选研究。我们建立了完全抑制最终胶体中纳米血小板杂质形成的生长条件，并证明了FAPbBr ₃的形成机理NCs通过将纳米血小板形成为瞬态物种而进行，而FAPbI ₃直接以立方形状的NCs形式形成。在对比CSPB（BR / I）_3个NCS，FAPb的稳定性（BR / I）_3个的NC与碘含量的增加。通过首先成核纯FAPbI ₃ NC，然后掺入溴离子来形成此类NC 。